Use option() to handle configuration variables, so they will show up in the CMake GUI


git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@577 632fc199-4ca6-4c93-a231-07263d6284db
diff --git a/configure.ac b/configure.ac
index 5454181..168f1d7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -261,7 +261,7 @@
 
 # SIMD is optional
 AC_ARG_WITH([simd],
-    AC_HELP_STRING([--without-simd],[Omit accelerated SIMD routines.]))
+    AC_HELP_STRING([--without-simd],[Omit SIMD extensions.]))
 if test "x${with_simd}" != "xno"; then
   # Check if we're on a supported CPU
   AC_MSG_CHECKING([if we have SIMD optimisations for cpu type])